# Copyright (c) 2002 Peter Guntert. All rights reserved.
## 7MACROS: window - apply commonly used window functions
##
## Usage: window cos
##        window cos2
##        window exp <L>
##        window gauss <L> <G>
##        window hamming
##        window hanning
##        window sin <phi>
##        window sin2 <phi>
##
## window is a standard macro that applies commonly used window functions,
## i.e. the data points s(k) (k = 1,...,n) are multiplied by a function f(t):
##
## window        function f(t)               remarks
## ------------- ------------------          ---------------------------
## cos           cos(pi/2*t)                 cosine window
## cos2          cos(pi/2*t)**2              cosine squared window
## exp <L>       exp(-pi*L*n*d*t)            exponential line broadening
## gauss <L> <G> exp(-pi*L*n*d*t*(1-t/(2*G)) Gauss-Lorentz window
## hamming       0.54+0.46*cos(pi*t)         Hamming window
## hanning       0.5+0.5*cos(pi*t)           "Hanning" window
## sin <p>       sin(r-(r-pi)*t)             shifted sine window
## sin2 <p>      sin(r-(r-pi)*t)**2          shifted sine squared window
##
## Parameters: pi = 3.14159...
##             n  number of data points
##             t  = (k-1)/n for data point k (k = 1,...,n)
##             L  line broadening parameter (in Hz)
##             d  value of the system variable delta, which should be 
##                set to the time increment (in s) between data points
##             G  the Gauss-Lorentz window has a maximum at t = G
##             p  shift in degrees
##             r  = p*pi/180
## 
## See also: multiply

if (nparam.lt.1) error "*** Error: Missing parameter."
p1 := '$p1'
if (p1.eq.'cos') then
  multiply cos(pi/(2*n)*(k-1))
else if (p1.eq.'cos2') then
  multiply cos(pi/(2*n)*(k-1))**2
else if (p1.eq.'exp') then
  p2 = -p2*pi*delta(active)
  multiply exp(p2*(k-1))
else if (p1.eq.'gauss') then
  p2 = -p2*pi*delta(active)
  p3 = 0.5/(p3*n)
  multiply exp(p2*(k-1)*(1.0-p3*(k-1)))
else if (p1.eq.'hamming') then
  multiply 0.54+0.46*cos(pi/n*(k-1))
else if (p1.eq.'hanning') then
  multiply 0.5+0.5*cos(pi/n*(k-1))
else if (p1.eq.'sin') then
  p2 = p2*pi/180.0
  multiply sin(p2-(p2-pi)/n*(k-1))
else if (p1.eq.'sin2') then
  p2 = p2*pi/180.0
  multiply sin(p2-(p2-pi)/n*(k-1))**2
else
  error "*** Error: Illegal window function \"$p1\"."
end if